1. Field of the Invention
The present invention relates to an electromagnetically actuated micromirror actuator and fabrication method thereof, and more particularly, to an electromagnetically actuated micromirror actuator having a two-axis freedom and actuated by the electromagnetic force and fabrication method thereof.
2. Description of the Related Art
Micromirror functions to change light path depending on the rotational degree of the mirror. This micromirror is widely used in optical switches, optical scanners, display and the like.
The conventional micromirror uses an actuator using electrostatic force. The electrostatic force is weak and therefore it is requested that the force constant of the torsion bars that are a portion to support the micromirror be small so as to rotate the micromirror at a desired angle. In this case, the torsion bars have to be thin, which make the micromirror brittle to an external impact, so that the operation of the micromirror is unreliable. In addition, in order to obtain a desired rotational angle, a large voltage above a few hundred volts is necessary. As one example of such application, there is disclosed a fabrication method of an optical micromirror using electrostatic force in U.S. Pat. No. 6,201,631.
Accordingly, the present invention has been devised to solve the above problems, and it is an object of the present invention to provide a micromirror actuator and fabrication method thereof which has a mechanically robust structure endurable against an external impact, enables a reliable operation having a large rotational angle, and being operable at a relatively low voltage.
To achieve the objects and other advantages, there is provided a micromirror actuator. The micromirror actuator includes: a substrate having a first penetration hole penetrating the substrate; a frame having a second penetration hole penetrating the frame, disposed inside the first penetration hole of the substrate, and connected with the substrate by first and second torsion bars formed to be bilateral symmetric around the frame; a micromirror disposed inside the second hole of the frame and connected with the frame by third and fourth torsion bars formed to be back and forth symmetric around the micromirror; first and second interdigitated cantilevers located between the substrate and the frame and protrudely formed from an inner wall of the first penetration hole to inside of the second penetration hole to be bilateral symmetric; third and fourth interdigitated cantilevers located between the substrate and the frame, protrudely formed from an inner wall of the first penetration hole to inside of the second penetration hole to be back and forth symmetric to the first and second interdigitated cantilevers; first and second interconnection lines respectively formed on the first and second interdigitated cantilevers and connected with each other, third and fourth interconnection lines respectively formed on the third and fourth interconnection lines to be connected with each other and having a current flow direction opposite to a current flow direction flowing through the first and second interconnection lines, and fifth and sixth interconnection lines that are bilateral symmetric to an imaginary line connecting the third torsion bar and the fourth torsion bar and respectively formed on the micromirror such that currents having opposite directions flow; first to fourth connecting bars connecting the first to fourth interdigitated cantilevers with the frame respectively; and first and second magnets respectively installed outside the substrate to be bilateral symmetric to the substrate and having different polarities from each other.
In accordance with another embodiment of the present invention, there is provided a method for fabricating the micromirror actuator. The method includes the steps of: (a) preparing an SOI substrate including an upper silicon layer, an oxide layer and a lower silicon layer; (b) etching the upper silicon layer to form the frame, the first to fourth torsion bars, the first to fourth interdigitated cantilevers, and the first to fourth connecting bars; (c) plating an interconnection line on the first to fourth interdigitated cantilevers and the micromirror; and (d) etching the lower silicon layer and removing the oxide layer such that the frame, the micromirror, the first to fourth torsion bars, the first to fourth interdigitated cantilevers, and the first to fourth connecting bars maintain only a predetermined thickness.